中文摘要：

采用电弧离子镀技术及后续热处理工艺在镍基高温合金上制备了均匀NiCrAlY涂层和梯度NiCrAlY涂层,分析了2种涂层的组织结构,对比研究了2种涂层静态空气下1000和1100℃恒温氧化行为以及1100℃的循环氧化行为.结果表明：均匀NiCrAlY涂层由γ′/γ相和少量β-NiAl相、α-Cr相组成,成分分布均匀;梯度NiCrAlY涂层具有外层富Al和内层富Cr的结构,其中外层由β-NiAl相和少量γ′/γ相、α-Cr相组成.一方面,梯度涂层的初始Al含量较高;另一方面,氧化过程中其富Cr区两侧出现了对富Al区的Al向基体扩散起阻碍作用的Cr（W）析出带.这两方面使梯度涂层长时间维持更多的Al存储相,提升了氧化膜的迅速生成及再生成能力,从而使涂层具有较好的抗氧化性能.

英文摘要：

MCrAlY（M=Ni and/or Co） overlay coatings are wildly adopted on hot components in gas turbine engines to protect them from rapid oxidation.Various methods can be applied to prepare MCrAlY overlay coatings,which formed by the arc ion plating method possess outstanding properties in terms of interfacial strength,porosity and componential distribution,and thus excellent oxidation properties.To increase the A1 content is deemed an economical and effective solution for enhancing the service performance and life for MCrAlY coatings at elevated temperature because the degradation process relies greatly on the ceaseless forming and spallation process of the protectiveα-Al_2O_3 scales during high-temperature oxidation.However,high content of A1 will lower the melting point and decrease the ductility of the coating.This phenomenon can be partly resolved through a gradient coating design.In this paper,a conventional NiCrAlY coating and a gradient NiCrAlY coating have been prepared by the combined method of arc ion plating and subsequent diffusion treatment on Nibase superalloy substrate.The microstructures,morphologies,isothermal oxidation behavior at 1000 and 1100℃and cyclic oxidation behavior at 1100℃have been investigated on the two kinds of the coatings.The results have revealed that the conventional NiCrAlY coating with uniform components is composed ofγ′/γphase,β-NiA1 phase and someα-Cr precipitate phase.While the gradient NiCrA1Y coating have showed layered microstructure,i.e.,an Al-enriched outer layer and a Cr-enriched inner layer,primarily consists ofβ-NiA1 phase,γ′/γphase and someα-Cr precipitate phase in the outer layer.During the oxidation,it is evident that the vanishment ofβ-NiA1 phase and the enlargement ofγ′/γphase for both the coatings.Nevertheless,the gradient coating has maintained higher Al content during long-term oxidation due to the massiveβ-NiA1 phase obtained in the outer layer after vacuum annealing and the Cr（W） zones precipitated beside the Cr-enriched inner layer du